In order to lower the costs and improve the performance of ICs (integrated circuits), the design nodes of ICs should be made smaller. Shrinking of the design nodes to 22 nm or even smaller, however, makes the defect inspection tool, such as an optical system, less able to detect the defects, owing to the optical resolution of light sources used being equal to or larger than the defect dimension. For advancing resolution in defect inspection, a more applicable inspection tool, such as an e-beam inspection tool, is provided for semiconductor process inspections. Further, in a VC (voltage contrast) mode of inspection the e-beam inspection tool can inspect for under-layer defects, the performance of which is almost impossible for current-day optical inspection systems to match. Hence, the e-beam inspection tool has become more important in the context of semiconductor processes.
Nevertheless, due to restrictions of the e-beam system per se, throughput thereof is much lower than that of optical systems. In order to increase throughput and VC inspection, larger currents, such as several hundreds nano-amperes (nA), are applied in the e-beam inspection systems. On the other hand, to increase the inspection resolution of the e-beam inspection system, small currents, such as several tens of pico-amperes (pA), are applied instead.
Up to the present day, there still is no single e-beam system that can handle both large current and small current inspections. A suitable means of using different e-beam systems for variant purposes while inspecting would definitely require more space (at least double the space) and more costs for the inspection. Therefore, there is a need for a new design of an e-beam inspection tool having the capability to handle both the large and small beam currents for handling both high resolution and high speed requirements.